How much do you know about the three common types of holes in PCBs

Drilling holes is a common process in PCBs (Printed Circuit Boards). It is used to conduct or connect copper foil lines between conductive shapes in different layers of the circuit board. Common types of drilled holes include through holes, blind holes and buried holes. Today, we will delve into the characteristics and uses of these three processes.

The first type is the through-hole (VIA), which is a common type of hole used to conduct or connect copper-clad lines between conductive shapes in different layers of a circuit board. Unlike blind and buried holes, a vias cannot be inserted into copper-plated holes for component leads or other reinforcement materials.

PCB circuit boards are made up of layers of copper foil stacked cumulatively. An insulating layer is placed between each layer of copper foil so that the layers cannot be connected to each other. In order to realize the signal connection of the circuit board,2 oz copper thickness in mm the through-hole is born.

Understanding the birth of the through-hole, let's take a look at its characteristics. In the production process of circuit boards, in order to meet customer demand, through-hole must be plugged. The traditional process of plugging holes in aluminum sheets was changed to use white mesh to complete the circuit board board surface soldermasking and plugging holes, in order to make the production more stable, the quality is more reliable, and the application is more perfect.

Through-hole is mainly used for circuit interconnection and conduction. With the rapid development of the electronics industry, the production process of printed circuit boards and surface mount technology requirements are increasingly high. In order to meet these requirements, through-hole plugging process came into being. At the same time, the through-hole also needs to meet the following requirements:

1. copper can be in the hole, soldermask can be plugged or not plugged. 2.

2. the lead hole must have tin-lead, to have a certain thickness requirements (4um), there shall be no soldermask ink into the hole, so as not to cause the hole has to hide the tin beads.

3. The lead hole must have solder resist ink plug hole, opaque, there shall be no tin ring, tin beads, as well as leveling and other requirements.

The second is a blind hole, as the name suggests, this hole is the PCB in the outermost layer of the circuit with the neighboring inner layer to plated holes to connect. Since this type of hole cannot be seen from the opposite side, it is known as a blind via. In order to increase the utilization of space between the layers of PCB circuitry, this will use a blind hole, that is, to a surface of the printed circuit board through the hole.

Blind vias are located on the top and bottom surfaces of the circuit board and have a certain depth, but do not punch through the board. It is mainly used for the surface layer of the line and the inner layer of the line below the link, the depth of the hole usually does not exceed a certain ratio (hole diameter).

Creating blind holes requires great care in drilling depth (Z-axis), as a slip can cause difficulties in plating the holes.plated through hole vs via Therefore, this method is rarely used in factories. However, it is also possible to drill the holes beforehand in individual circuit layers and then glue them together at the end. This approach requires the use of a precision positioning alignment device.

The third type is buried holes, which are links between any circuit layers inside the PCB, but do not lead to the outer layer or extend to the surface of the board.

Buried holes cannot be achieved by drilling after gluing, but must be drilled directly in the individual circuit layers. Partial bonding of the inner layer is followed by plating and finally full bonding. Compared to the previous through holes and blind holes, buried holes are more labor intensive and therefore more expensive. This process is usually only used for high-density circuit boards to increase the space available for other circuit layers.

Drilling is a very important step in the PCB production process and should not be done in a sloppy manner. Drilling is the process of drilling the required perforations in the copper-clad board to provide electrical connections and secure the devices.

If the operation is not correct, the hole process problems, the device will not be fixed on the circuit board. If it is not done properly, the device will not be fixed on the board, which may affect the use of the board, or the whole board will be scrapped. Therefore, the drilling process is quite important.